Storage battery separator



Patented Aug. 10, 1943 Bruno H. Schubert, We

to National Lead Serial No. 267,923, now Patent No.

dated July 21, 1942.

The present application is a'division of my copending application, Serial No. 267,923, filed April 14, 1939, which issued as U. S. Patent No.

I 2,290,496 on July 21, 1942.

The invention herein described and claimed relates to storagebatteries of the lead-acid type,

ehawken, N. J., assi g'nor' mpany, New York,'N. Y., a corporation of New Jersey N'. Drawing. Original application April 14, 1939,

Divided and this application October 2, 1941, Serial No. 418,299

6 Claims. oi-1364149) p, jute, corncobs, bagasse, humus, peat moss, etc. The so-called waste sulflte liquors obtained from the manufacture of paper or solutions resulting from caustic alkali or inorganic particularly having reference to the use in such types of storage batteries of an improved separa tor manufactured according to the method herein described. The obiects of the invention include, among others, the manufacture of an im proved type of storage battery separator as well as the use of such improved separator in stor age batteries of the lead-acid type, thereby to impart to the storage battery an improved discharge capacity and a longer life. The novel separators of the present invention are characterized in that they contain as an integral part thereof an added active organic ligneous compound By the term organic ligneous compound as used in the description of the present invention,

are meant all those organic materials of extreme- 1y complex chemical nature which are present in all forms of vegetable matter other than the cellulose, fats, waxes, resins, wood acids and salts of wood acids, and said term embraces the :derivatives of such complex chemical materials, addition and decomposition products thereof. It is not possible to state what is the true chemical nature of lignin or of organic ligneous materials; chemical science has not yet determined the structure thereof. It is known, however, that when substances-of vegetable origin are suitably treated with acidic materials such as calcium acid suliite, alkalies or some organic solvents,

such as dioxane, there are obtained solutions containing among other thingssome of the ligneous materials originally present in the vegetable substances. Separated irom the naturally occurring fats, waxes, resins, wood acids and salts of wood acids also present in the vegetable substance the organic ligneous materials, I have found, possess properties which are conductive to better battery performance when added to separators, and I have designated such ligneous compounds in the description of the present invention and in the appended claims as active organic ligneous materials. such a designation will serve to dis tinguish over those unextracted inactive ligneous compounds which are originally found and which remain, after treatment, in the structure ofthe wood. Inasmuch as these organic ligneous compounds are present in all forms of vegetable substances, the particular type of vegetable substance from which the active organic ligneous compound is derived is of no consequence in the practice of the present invention. Wood is a very convenient source for obtaining these active organic ligneous compounds, as are also straw,

acid processes for treating wood or wood pulp, are

a readily .available source of organic ligneous compounds, useful in the practice of the invention. 0n the whole, the sources from which active organic ligneous materials may be derived are well understood by those skilled in the art.

It has been known, prior to our invention, that if lignin and ligneous materials be incorporated into the negative plate of a lead-acid type storage battery, certain desirable eiiects, in thenature of greater discharge capacity, were imparted to the storage battery. In the manufacture of storage battery separators the most commonly employed material used up to now has been wood. A separator fashionedfrom wood is treated, for example, with caustic alkali solutions, to remove from the wood the naturally present fats, waxes,

resins, wood acids, salts of wood acids and some oi the ligneous materials because the art had observed that such compounds as present in the wood in their original states are subject to hydrolysis in the storage battery to the detriment thereof. The so-treated separator, as employed by the prior art, was therefore substantially free because it is firmly combined with the cellulose structure of the wood. At any rate, this socalled hemicellulose ligneous organic combination apparently is inefiective in producing improved separators, and I have-found it to be necessary to add the so-called active ligneous'material to the'treated Wood separators in order to-impart to I a storage battery improved life and low temperature capacity.

Therefore, it should be understood that untreated wood separators do not exhibit the improved properties' of my treatedseparators, and that the ligneous material originally available in the wood is not in the proper active form to producethe desired improvements. Furthermore, it has been found desirable, in the practice of my invention, to effect a uniform distribution of the active, ligneous compounds over the surfaces of the separators with sufiicient penetration to anchor the products when the organic is set by the acid fixing treatment.

Thus, I have now found that if active organic ligneous compounds prepared according to the present invention aremade a part of a battery separator. for instance, by impregnating a wooden separator of the prior art or by compounding these materials into a composition separator, the resulting separator has the unusual property of imparting greater discharge capacity and a longer life to the storage battery.

The manufacture of a wood separator for use in a storage battery according to the methods of the present invention will now be further described for illustrative purposes, it being understood that my invention is not limited to wooden separators, but embraces all types of battery separators which contain as an integral part thereof added active organic ligneous compounds.

A preformed wood separator of the present commercial type, i. e., one which has been subjected to a treatment, e. g., caustic soda treatment, to remove organic fats, waxes, resins, wood acids, salts of w od acids and some of the readily soluble organic ligneous compounds, etc., is immersed in a so ution of active organic ligneous compounds. The solution of active organic ligneous compound may be obtained by any of the suitable means above described. For purpose of this illustration, the active organic ligneous solution may be derived from a waste sulfite liquor or a caustic alkali liquor obtained from papermaking processes. Preferably the solution containing'the separator is heated to'hasten absorption of the active organic ligneous compounds by the separator. Generally speaking, the higher the heat, the greater will be the rate of absorption, but the temperature should preferably be not higher than that of boiling water. Thus, temperatures between 70 and 212 F. are very suitable to the practice of the invention. The processing may be carried out at atmospheric pressure, or if desired, the impregnation may be carried out under pressure in an autoclave.

The concentration of the active organic ligneous compound solution is not critical; for example, waste sulfite liquors or caustic alkali llquors, treated in known manner to render them 7 substantially non-frothing and non-sulfating obtained from paper making processes and containing the usual 10-12 per cent of solids, may be used. Impregnation should be carried out until, as determined by test, the separator Has-absorbed a desired amount of active organic ligneous material. Only a small amount of absorbed active organic ligneous material gives the improved results of the invention. Amounts between 0.01 per cent and 5 per cent of the weight of the separator, preferably between 0.25 and 2.0 per cent constitute a practical range within the scope of the invention. As will be appreciated, the solution of organic ligneous compound should be as free as possible of objectionable organic or inorganic salts which might interfere with the proper functioning of the ligneous com-pound or separator.

After the separator has been impregnated as described, the active organic ligneous compound is preferably fixed in the separator by treatment with a suitable fixing agent. Among those best suited for this process are solutions of sulfuric acid of a strength which may vary between 5 and per cent, depending upon the type of ligneous compound tobe employed. For general purposes, the strength of sulfuric acid fixing solution should be between 15 and 30 per cent.-

Salts, particularly ionizable salts, includin those of lead. or even suspensions of lead compounds such as litharge, also exert a "fixing" action upon the active ligneous compound absorbed by the separator. So also do solutions of salts, the electro-positive element of which precipitates ligneous compounds'from their solutions. The fixing treatment may also be advantageously carried out at an elevated temperature, say, between '70 and 212 F. Furthermore, the fixing" treatment may not necessarily follow the impregnation and the impregnated separators may be dried and stored for some time before treatment with the fixing agent, depending upon the components of the separator. After washing and drying, the so-treated separator is ready for use in a storage battery. The fixing treatment is especially recommended when the separator after impregnation with the active organic ligneous compound is stored prior to use or is separately prepared by the separator manufacturer and shipped to the storage battery maker. However, when separators are prepared in the storage battery plant and directly used in the battery, the fixing treatment may be dispensed with, but should the active organic ligneous compound exhibit a tendency to bleed out of the separator into the weak acid electrolyte, which may be encountered when the plate-forming acid is absorbed by the unformed plates, a fixing treatment should be employed. The separator thus manufactured will have the active organic ligneous compound evenly deposited on the surface and uniformly distributed throughout the pores thereof.

In connection with the foregoing, it should be pointed out that the impregnating solution of active organic ligneous compound may be either an aqueous solution, an acid, alkali or organic solvent solution.

In the manufacture of composition separators, for example, those made by pressure operations, the active organic ligneous material compounds in the form of dry powder may be mixed directly with the materials from which the separator is formed and the separator fabricated in the usual manner.

Bagasse, pressed fiber separators, spun glass, or glass-fibre separators which are adaptable to be impregnated, or to which the organic solution may adhere, may be subjected to an impregnation treatment substantially the same as that described in connection with wood separators.

Now, in order that those skilled in the art may appreciate the advantages of this invention, the following specific embodiments are given, but only for illustrative purposes:

Example I A batch of the regular wood separators of commerce, that is, those having been treated to remove fats, waxes, resins, wood acids, salts of wood acids, and some of the ligneous materials, were digested at atmospheric pressure for one hour at a temperature of about F. in an active organic ligneous compound in a 5 per cent sulfuric acid solution, having a specific gravity of about 1.063 and containing grams of active organic ligneous compounds in 800 cc. thereof. After this digestion treatment, the separators were immersed in a sulfuric acid solution of about 25 per cent strength at about 120 F. for 30 minutes in order to fix the active organic ligneous compounds into the pores of the separator. After the fixing treatment, the separators were washed.

Example II A batch of composition rubber separators was subjected to the same treatment as described in Example I.

Example IV A batch of composition rubber separators was subjected to the same treatment as described in" Example II.

The separators obtained from these four examples, were made up into standard type leadacid storage batteries. These batteries were then subjected to a standard discharge test in comparison with other batteries made up with untreated wood separators from the same stock as were used for Examples I and II- as well as batteries made up with untreated composition rubber separators from the same stock which were usedfor Examples III and IV. The technique'on the tests were as follows:

The batteries undergoing automatic life tests were subjected to a discharge of 300 amperes at F. and a cut-out of one volt per cell or 3 volts for the entire battery. When the battery was'completely discharged, it was fully charged and again discharged under the same test conditions, the discharge and charge being considered as one cycle. As the cycles of discharge and charge follow one upon the other, the duration of time of the discharge portion of the cycle becomes shorter, so that after any given number of cycles that battery whose discharge output is greater than another battery is said to have a better low temperature capacity characteristic.

Under these conditions the results obtained in Where expanders are used in the negative plates in conjunction with the present invention, it appears that the effect of the improved separator makes itself felt most prominently about the time the effect of the organic expanders of the negative plate begins to be dissipated.

When the novel separators of the present invention are incorporated into storage batteries of the lead-acid type, batteries are obtained which possess greater discharge output capacity and longer life, especially at low temperatures, which, over a 300-350 cycle life test period, is seldom less than 40 per cent greater than a similar battery containing the separators of the prior art and in many cases is as much as 100 or more per cent greater. v

By virtue of the improved results above set forth, it is easily possible to distinguish between my improved separators and those of the prior art. However, a simpler and quicker test for identifying my improved separators from those of the prior art is to cut up the respective separators and treat the pieces with a 2-3% caustic soda solution. The extracted matter dissolved from my improved separator will, because of the presence of the added active organic ligneous compolund, impart to the caustic soda solution a considerably intensified color which will be lacking in the case of ordinary separators.

Having thus described my invention, I claim the following as new and useful:

1. A storage battery separator substantially free from naturally occurring fats, waxes, resins,

wood acids and salts of wood acids and having active organic ligneous compound.

testing the batteries prepared with, the separators obtained according to Examples 1 to 4 and those obtained with batteries containing untreated separators were as follows:

Table Duration of discharge No. of portion of cycle-seconds cycles Treated Untreated Wood se arators 253 240' 125 Compos tion separators; 253 200 80 The improved result of our invention is most pronounced at the period when it is most needed, namely, after numerous cycles of discharge and charge and particularly effective under the most severe operating conditions, viz.-, cold .weather.

Furthermore, the improved result is not depend- 2. A storage battery separator substantially free from naturally occurring fats, waxes, resins, wood acids and salts of wood acids and having evenly deposited on its surfaces and uniformly distributed throughout its pores a small added amount of an active organic ligneous compound.

. 3. A wood storage battery separator substantially free from naturally occurring fats, waxes, resins, wood acids and salts of wood acids and im- I pregnated with a small added amount of an active organic ligneous compound.

4. A wood storage battery separator substantially free from naturally occurring fats, waxes, resins, wood acids and salts of wood acids and containing a small added amount of an active organic ligneous compound.

5. A wood storage battery separator substantially free from naturally occurring fats, waxes, resins, wood acids and salts of wood acids and having incorporated'therein an added active organic ligneous compound in an amount between about 0.01 per cent and about 5.0 per cent based on the weight of the separator.

6. A wood storage battery separator substan- I tially free from naturally occurring fats, waxes, resins, wood acids and salts of wood acids and having incorporated therein an added active organic ligneous compound in an amount between about 0.25 per cent and about 2.0 per cent based on the weight of the separator.

BRUNO H. BCHUBER'I'.

incorporated therein a small added amount of an 

